update url for qemu.

Signed-off-by: wanlinwang <32032219+wanlinwang@users.noreply.github.com>

Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>

Since musl is already incorporated into the build system (see for
example configure.ac, Makefile.in), this patch adds a submodule for
musl based on the current v1.2.2 release.
The GitHub Actions configurations have also been updated to include
the musl based toolchain.

Signed-off-by: Florian Hofhammer <florian.hofhammer@fhofhammer.de>

Both the glibc and newlib submodules are already pointing to the
upstream repositories where development happens.
Since they are therefore not referring to RISC-V specific forks,
this patch unifies the directory naming by only prepending the
"riscv-" prefix to submodules that point to repositories in the
riscv-collab Github organization.

Signed-off-by: Florian Hofhammer <florian.hofhammer@fhofhammer.de>

Signed-off-by: Christoph Muellner <cmuellner@linux.com>

Drop riscv-qemu, add upstream qemu, and fix one Makefile reference.

Adopt the path of qemu to relative paths too.

Binutils and GDB are kept in the same repository but follow seperate
relaese streams.  We've been release GDB versions based on binutils
tags, but this is the wrong thing to do and has caused multiple
headaches related to our out-of-tree GDB port.

This patch splits the binutils and GDB submodules, but doesn't actually
change the versions.

We need QEMU to run the test suite.  This patch automates the build so
I don't need to keep remembering how to do it by hand.

This also adds a submodule pointer to the RISC-V DejaGnu port, which is
required to run the GCC test suite.  The DejaGnu port only supports the
GDB simulator.  A bunch of tests fail right now, but that's expected.

As we prepare binutils for upstreaming we want to start closely tracking
upstream changes.  There's a riscv-binutils-gdb repository that contains
the binutils port, and I want to centralize all the development there.
This commit uses that repository instead of the patches that used to
live here, so we're less likely to lose patches.